Purpose To study pathomorphological and immunohistochemical characteristics of small cell malignant tumor(SCMT) of bone.

Background and Objective: The treatment and prognosis of extrapulmonary small cell carcinoma (EPSCC), a uncommon malignant tumor, have seldom been reported.

KRAS mutation frequency in tumor tissue, can be predicted non-small cell lung cancer molecular targeted therapy efficacy and prognosis, and molecular inhibitors of RAS genes is still in its infancy.